The invention relates to the use of puroindolines as additive in biscuit manufacture.
Puroindolines are proteins which are present in wheat grain and which have the capacity to interact with lipids. Two isoforms of puroindolines, respectively called puroindoline a and puroindoline b, have been characterized. They are basic proteins (pI xcx9c10) of low molecular weight (about 13 kDa); they comprise 10 cysteine residues, forming 5 disulfide bridges, and a domain rich in tryptophan residues [BLOCHET et al., in: xe2x80x9cGluten Proteins 1990xe2x80x9d; (BUSHUK W. and TKACHUK R., eds), AACC, St Paul Minn., pp 314-325 (1991); BLOCHET et al., FEBS Lett., 329: 336-340, (1993).
Moreover, a recent publication [GIROUX and MORRIS, Proceedings of the National Academy of Sciences, vol. 95 p. 6262-6266, (1998)] indicates that the protein called friabilin, considered as a biochemical marker for wheat grain hardness [GREENWELL and SCHOFIELD, Cereal Chem., 63, 369-380 (1985)], is a heterodimer of puroindolines a and b which is involved in controlling the hardness of the endosperm.
Puroindolines possess specific surfactant properties linked to their high affinity for lipids; they have in particular a high foaming power which is increased in the presence of polar lipids [DUBREIL et al., J. Agric. Food Chem., 45: 108-116 (1997); WILDE et al., J. Agric. Food Chem., 41, 1570-1576 (1993)]. It has thus, for example, been shown that the addition of puroindoline made it possible to restore the foaming properties of beer supplemented with stearic acid, phospholipids or triglycerides [CLARK et al., J. Inst. Brew. 100, 23-25 (1994)], or those of egg white supplemented with oil [HUSBAND et al., in: xe2x80x9cFood Macromolecules and Colloidsxe2x80x9d (DICKINSON E. and LODENT D., eds), Royal Society of Chemistry, London, pp. 285-296, (1995)].
Recent work relating to the potential applications of the properties of puroindolines in the context of the manufacture of bread shows that the addition of a small quantity of puroindoline (0.1% relative to the weight of the flour) considerably modifies the rheological properties of the dough and the structure of the bread crumb [DUBREIL et al., Cereal Chem. 75, 2: 222-229, (:998)]. however, the effect of puroindolines on the volume of the final product after baking varies markedly according to the baking quality of the flour used (which is linked for a large part to its glutenin composition). When puroindolines are added to flour with good baking quality, a reduction of the order of 10% in bread volume (in other words an increase in its density) is observed compared with bread made without addition of puroindolines; this decrease in volume reaches 20% if flour of poor baking quality is used. On the other hand, if puroindolines are added to flour of average baking quality (resulting from the mixing of the above two), an increase in bread volume of the order of 20% is observed.
The inventors have undertaken the study of the effect of puroindolines on preparations which are more complex than bread dough, such as the doughs normally used in pastry and biscuit manufacture.
They have thus observed that the addition of puroindoline during the preparation of biscuits induced a significant effect on the texture and/or the density of the finished product, and that it was possible to independently control these two parameters.
The subject of the present invention is the use of puroindoline as additive which makes it possible to control the texture and/or the density of a biscuit.